150 NATURAL SCIENCE [September 



very small. These results are due, on the one hand, to the luxuriant 

 growth of corals, and on the other hand, to the actual scarcity of the 

 bottom flat-fish or pleuronectids, which with the allied gadoids form 

 the most important elements of our northern fisheries. 



The scientific results are of some value. It is to be noted that 

 in many cases in which the lead indicated a sandy bottom, the trawl 

 showed the presence of dense masses of coral, a fact which should be 

 noted by coral-reef theorists. Mr J. E. Duerden, of the Jamaica 

 Museum, gives an able summary of the fauna. Bcrgia, an actino-zoan 

 commensal with a sponge, was re-discovered, and sponges and alcyon- 

 arians were found in great abundance. The edible fishes were not 

 abundant, either in actual quantity or in number of species. Mes&prion, 

 Ocyurus, Haemvlon, and Serranus appear to be the most important. 



Apparently the local supply in Jamaican waters will in future, 

 as heretofore, have to depend upon the use of lines and drift-nets. 



ASCIDIANS AND BlPOLAEITY 



We have more than once directed attention to striking cases of 

 distribution, indicating some connection between the North Pacific 

 and North Atlantic. Now comes Professor Herdman (Trans. Liver- 

 pool Biol. Soc, xii., pp. 248-267, pis. xi.-xiv., June 1898) and draws 

 up lists of closely-allied species of ascidians from Puget Sound and 

 our own N. Atlantic coasts ; similar series are, he says, shown in 

 a subsequent paper on the Crustacea by Mr A. 0. Walker. " This, 

 taken along with the similaritv between the two faunas shown in 

 other groups, suggests the possibility that there is a common 

 northern circum-polar marine fauna which sends extensions south- 

 wards on the western coasts of Europe and America," 



Such a conception is of course opposed to the well-known hypo- 

 thesis of Sir John Murray that the marine faunas towards the poles 

 are genetically more closely related to each other than to any inter- 

 vening fauna. Sir John has supported this ' bipolar ' hypothesis 

 by quotations from the reports of some of the specialists who 

 described the " Challenger " collections. It has struck us that this 

 somewhat crude lumping of the conclusions of many minds, ex- 

 pressed originally with very different ends in view, could lead to 

 no secure result, and we are by no means surprised to rind Mr 

 Herdman commenting as follows : — " I do not know how it may be 

 with other authors quoted, but in my case the series of short 

 extracts given from my report require to be expanded and explained, 

 and are then seen not to give Dr Murray's view the support which 

 he supposes. My remarks, on p. 265 of the Report, which he 

 quotes, refer only, it may be stated, to 'Challenger' species. 

 In the genus Styela, for example, there are plenty of species 

 known from the tropics. Dr Sluiter has described about fifteen 



